We have investigated the interaction of lipoproteins with liposomes to form recombinant particles. A number of lipoprotein fractions (VLDL, IDL, LDL, and HDL) all disrupt liposome stucture by an essentially irreversible and qualistoichometric process. In the case of HDL, the major apoprotein, A-I, recombines with dimyristoyl phsophatidyl choline vesicles 40:1 lipid-protein to form discs approximately 100 Angstroms in diameter and 32 Angtroms in thickness, with proteinon the rim. These structural results were obtained by a combination of neutron scattering, electron microscopy, and column chromatography. With dipalmitoyl phosphatidylcholine, A-I also forms what we term "vesicular recombinant" particles in a process which may related to physiological mechanisms by which proteins are assembled into membranes and lipporoteins. To study this process we have developed a technique called "phase transition release" (PTR) which is also being applied to study incorporation of tubulin into membranes. Liporoteins were lebelled with the fluorescent lipid 3,3 dioctadecylindo-carbocyanine for studies of interaction will cell surface liprotein receptors. The lipoproteins are also being labelled with NBD lipids for two-color fluorescence identification of cells in atheroscleroic plaques.